1. Field of the Invention
The present invention relates generally to compositions that contain copolymers of vinyl monomers. More specifically, the present invention is directed to compositions that contain functional copolymers containing olefinic monomers and thermosetting compositions thereof.
2. Description of Related Art
Functional polymers used in liquid, powder, and electrodepositable coating compositions are typically random copolymers that include functional group-containing acrylic and/or methacrylic monomers. Such a functional copolymer will contain a mixture of polymer molecules having varying individual functional equivalent weights and polymer chain structures. In such a copolymer, the functional groups are located randomly along the polymer chain. Moreover, the number of functional groups is not divided equally among the polymer molecules, such that some polymer molecules may actually be free of functionality.
Additionally, attempts to introduce functionality into acrylic or methacrylic ester containing homopolymers and copolymers by reacting the polymer with an appropriate functional compound after polymerization can result in the formation of cyclic structures along the polymer backbone where acrylic and or methacrylic residues are positioned next to each other along the polymer chain, i.e. nearest neighbors. The formation of cyclic structures occurs when nearest neighbor acrylic or methacrylic residues each react with a functional group in the functional compound resulting in a pendant linkage between the nearest neighbor acrylic or methacrylic residues. The result is a loss of functionality in the polymer as well as an undesirable change in physical properties such as glass transition temperature, solubility and compatibility with other materials.
As an example, in thermosetting compositions, the formation of a three-dimensional crosslinked network is dependent on the available functionality, the functional equivalent weight as well as the architecture of the individual polymer molecules that comprise it. Polymer molecules having little or no reactive functionality (or having functional groups that are unlikely to participate in crosslinking reactions due to their locations along the polymer chain) will contribute little or nothing to the formation of the three-dimensional crosslinked network, resulting in decreased crosslink density and less than optimum physical properties of the finally formed thermoset coating.
It would, therefore, be desirable to provide compositions that include functional acrylic and/or methacrylic copolymers that are free of undesirable cyclization reactions and provide unencumbered access to the functional groups therein to participate in desired reactions, such as thermosetting and curing reactions.